Some image reading devices are configured to collectively read a plurality of source documents placed on a document table, and automatically crop each of the source documents, as individual images independent from each other (what is known as multi-cropping function).
The mentioned function is further utilized to read a plurality of source documents (e.g., business cards) placed on the document table of the image reading device, and again read the plurality of source documents reversed by a user. Then pair identification is performed, by comparing the positions of the respective images of the source documents that have been reversed, with the positions of the respective images of the source documents unreversed yet, to thereby identify a pair of images the positions of which are closest to each other, as an image pair that represents the front and back faces of the same source document (see, for example, PTL 1 and 2).